Strong metal-support interactions are an important issue in determining the catalytic activity of heterogeneous catalysis. Here, we investigated the effect of the support in two-dimensional Pt nanocatalysts on reducible metal oxide supports under CO oxidation. Several reducible metal oxide supports, including CeO2, Nb2O5, and TiO2 thin films, were prepared via the sol-gel technique. The Langmuir-Blodgett technique and arc plasma deposition (APD) process were employed to obtain Pt nanoparticle arrays with and without capping layers, respectively, on an oxide support. We found that reducible metal oxide supports have a uniform thickness and crystalline structure after annealing, and exhibit a bandgap of 3.4-4.2 eV. We tested the catalytic performance of CO oxidation over Pt nanoparticles supported on metal-oxide thin films under 40 torr CO and 100 torr O-2. The catalytic activity of the Pt nanoparticles on oxide supports showed the general trend of CeO2 > Nb2O5 > TiO2 > SiO2 for both the colloidal and APD Pt nanoparticles. These results reveal a strong support effect on the catalytic activity of the two-dimensional Pt nanocatalysts on oxide substrates under CO oxidation, with possible applications of tuning catalytic activity by engineering metal-oxide interfaces. (C) 2014 Elsevier B.V. All rights reserved.